1. Field of the Invention
The invention relates to the repair of accidentally severed nerves and more particularly to a method and means for accomplishing this end.
2. Description of the Prior Art
The method and means of the present invention may have a wide variety of applications including vascular repair and the like. While not intended to be so limited, for purposes of an exemplary showing the invention will be described in its application to the repair of severed mammalian peripheral nerves.
Many methods have been utilized to promote or facilitate nerve regeneration in peripheral nerve injuries. Unfortunately, despite advanced surgical techniques and use of the operating microscope, the results of peripheral nerve surgery in general have not improved greatly.
The problem of peripheral nerve regeneration has been studied intensively by many investigators and has been found to depend on many factors. The most important of these are the patient's age, type of injury, length of the nerge gap, nutrition of the nerve, amount of scar tissue, and finally, the technique of nerve repair. A repair is satisfactory when it is executed with as little trauma as possible and when anatomic approximation is achieved. It is difficult to fulfill the requirements without magnification, micro-surgical instruments, and the finest of sutures. Despite the advances that have been made to date, the re-establishment of normal function in the damaged nerve is considered poor. If results are to improve, in addition to gaining greater understanding of the physiology, the pathology of neural tissue and processes of nerve regeneration, it will be necessary to attain greater sophistication in the surgical manipulation of nerve tissue. It is to this latter goal that the present invention is directed.
While not so limited, the present invention is particularly advantageous in the repair of small nerves, that is, nerves 2 mm in diameter and less. Prime applications of the method of anastomosis of the present invention are the repair of digital and facial nerves. Digital nerves are the most frequently severed peripheral nerves, and though small in size are of critical importance because of their properties of discriminatory touch. Injury to facial nerves, though less common, is of serious consequence because of loss of communication through expression, interference with speech and activities as eating, drinking, and the like, as well as psychological effects.
The most critical factor of technique in neurorrhaphy is the accurate approximation of the cut ends of the fascicles (nerve bundles within the nerve trunk). Even though other factors may be ideal, the neurorrhaphy will fail if a significant number of fascicles do not match up. This is because motor axons regenerating through the sheaths of sensory nerves and vice versa will give no return of sensory or motor function. The fascicles of the larger nerves, such as the median and ulnar nerve, are large enough in cross sectional area that the cut ends of individual fascicles can be matched up by using the epineural vascular pattern for rotational orientation and microsurgical suture techniques. The fascicles of the small diameter nerves, however, are too small to be matched by suturing. The best that can be done is to match the nerve ends epineurium to epineurium using recognizable vascular patterns for rotational positioning. If the peripheral nerve is cleanly severed, a primary repair can be made with good approximation of the fascicles. However, if a segmental deficit exists, the likelihood of surgical orientation or matching of fascicles becomes increasingly less the greater the gap. This is attributed to the twisting and plexiform course of the fascicles and axons within the nerve trunk. It is apparent then, except in the instance of a clean cut followed by a primary repair, that a repair of a small nerve, successful in all other respects, will depend on the chances that the fascicles will match up, unless some natural mechanism exists for directing the axons to sheaths of their own kind. The problem of matching fascicles becomes less significant with the smaller nerves, since there are fewer fascicles, often no more than one, to contend with. Thus the chief hazard to the successful repair of fine nerves is the trauma produced by sutures and manipulation of the nerve and invasion of the field of regeneration by epineural and extraneural connective tissue. Many attempts have been made, almost entirely with larger nerves, to shield the region of anastomosis from connective tissue and facilitate longitudinal directional growth of the epineural and nervous tissue.
Of particular interest has been the use of other tissues or materials to form a channel through which the nerve fibers may grow and bridge the gap between the cut ends. Severed nerves have been drawn through blood vessels, or through decalcified bone tubes. Nerve fibers have also been wrapped in sheets of rubber, cargyl membrane, fascia lata or various other materials in an effort to reduce the ingrowth of scar tissue between the ends of the severed fibers. The methods employing organic materials have been relatively unsuccessful, largely because phagocytes have removed the nerve covering prematurely. More recently a tubulation method has found some success in neurorrhaphy whereby sheets of Silastic are wrapped about the anastomosis. This method facilitates regeneration of nerves, but suffers from the drawback of requiring the use of sutures. Methods employing adhesives, especially the cyanoacrylates, as a sutureless technique to anastomose severed nerves, though highly attractive have so far been ineffective.
The method and means of the present invention overcomes the above noted problems. The use of a porous bridge-conduit or tube prosthesis permits the cut ends of the nerve to be gently drawn into optimal proximity and secured in position without undue traumatic manipulation. Further, the prosthesis serves to reduce the effect of connective tissue (scar tissue), prevent neuromas, reduce edemal swelling and at the same time allow for escape of fluid exudates. The operational procedure is simple and can be quickly adapted by surgeons relatively inexperienced in performing neurorrhaphies.
The usefulness of such a prosthesis is obvious in any peripheral nerve injury or multiple injuries to the same nerve. It provides a stable bridge-conduit or tube for the regenerating proximal stump to grow through while retarding invasion of the tube by scar tissue.